Preparation method and application of metal organic framework material

Abstract

The invention provides a preparation method and application of a metal organic framework material. The preparation method comprises the following steps: carrying out first reaction on fumarate and aluminum salt in an aqueous medium to obtain a suspension; adding polyethyleneimine into the suspension, and carrying out a second reaction; after the second reaction is finished, carrying out post-treatment to obtain a polyethyleneimine modified aluminum fumarate (AlFuPEI) metal organic framework material; the fumarate and the aluminum salt are both water-soluble; the molecular weight of the polyethyleneimine is 8000 to 30000 Da; the mass ratio of the polyethyleneimine to the fumarate is 1: (5-15); the post-treatment comprises ultrasonic treatment and freeze drying. The AlFuPEI material provided by the invention has excellent anionic dye adsorption performance, and has a definite industrial application prospect in the field of deep treatment of dye wastewater.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, specifically relating to a method for preparing a metal-organic framework material, and more particularly to a method for modifying an aluminum fumarate metal-organic framework with polyethyleneimine, as well as the materials obtained by this method and their applications. Background Technology

[0002] The rapid development of the textile, dyeing, and leather industries has led to a surge in dye wastewater discharge. Statistics show that approximately 20% of global industrial wastewater originates from dye-related industries. Among this wastewater, azo dyes (such as Congo Red) pose a serious threat to the ecological environment and human health due to their high toxicity, recalcitrant nature, and carcinogenicity. Traditional dye wastewater treatment methods (such as biodegradation and chemical oxidation) suffer from low efficiency and are prone to secondary pollution. Therefore, developing efficient, economical, and environmentally friendly wastewater treatment technologies is of great significance.

[0003] Adsorption methods are widely studied due to their ease of operation, but traditional adsorbent materials (such as activated carbon and zeolites) often suffer from drawbacks such as low adsorption capacity (typically below 200 mg / g), poor selectivity, and difficulty in regeneration, limiting their practical applications. Metal-organic frameworks (MOFs) are considered highly promising adsorbent materials due to their ultra-high specific surface area, tunable pore structure, and abundant surface functional groups. However, most MOF materials carry a negative surface charge, resulting in electrostatic repulsion with similarly negatively charged anionic dyes, leading to unsatisfactory adsorption performance for these dyes. Furthermore, some MOFs also suffer from poor water stability, high preparation costs, and difficulties in reusability.

[0004] Aluminum fumarate (AlFu) metal-organic frameworks are microporous materials composed of angle-sharing metallic octahedrons linked by fumarate, with a pore size of approximately 5.7 × 6.0 Å. 2(Angew. Chem. Int. Ed. Engl. 2015, 54, 3664-3668) This material can be used in fields such as carbon dioxide capture and dye adsorption. Azhdari et al. (J. Environ. Chem. Eng., 2019, 7, 103437) reported a method for synthesizing aluminum fumarate MOF materials via a hydrothermal method and combining them with graphene oxide or reduced graphene oxide for adsorption and removal of Congo red dye. The composite material obtained by this method has an extremely limited adsorption capacity for dyes, with an adsorption capacity for Congo red not exceeding 200 mg / g. Wang et al. (ACS Omega 2020, 5, 50, 32286–32294) reported a method for modifying the metal-organic framework material NH2-MIL-101(Al), prepared with aluminum ions as the metal center and 2-aminoterephthalic acid as the organic ligand, with low molecular weight (600 Da) polyethyleneimine (PEI). NH2-MIL-101(Al) is a mesoporous material with two main types of cage-like channels, where the free diameters of the small and large cages are approximately 29 Å and 34 Å, respectively. The modified PEI@NH2-MIL-101(Al) composite material exhibits good anionic dye adsorption performance, with adsorption capacities of 894 mg / g for methyl orange and 998 mg / g for DR80. However, this modification method is difficult to extend to other MOF materials (especially microporous ones) to achieve similar results. On the one hand, if PEI is used to modify microporous materials, especially when a higher molecular weight PEI is desired to increase the amino group density, pore blockage is likely to occur, leading to a deterioration in material performance. On the other hand, PEI-modified microporous MOF materials prepared under conventional methods are only suitable for adsorbing small-sized anions. For example, CN104785210A discloses a method for modifying UiO-66 with PEI to improve its adsorption capacity for small-molecule inorganic anions such as phosphate and arsenate in water.

[0005] To address the aforementioned issues, it is necessary to develop a method for preparing PEI-modified aluminum fumarate metal-organic framework materials. Summary of the Invention

[0006] This application aims to provide a method for preparing metal-organic framework materials, which can be used to obtain metal-organic framework materials with high adsorption capacity, excellent selectivity and cycle stability, and can achieve efficient treatment of anionic dye wastewater.

[0007] To achieve the above objectives, this application provides the following technical solution: A method for preparing an AlFu-PEI metal-organic framework material includes the following steps: a) The fumarate and aluminum salt are reacted in an aqueous medium to obtain a suspension; b) Add polyethyleneimine to the suspension to carry out the second reaction; c) After the second reaction is completed, post-processing is performed to obtain the AlFu-PEI metal-organic framework material; Both the fumarate and aluminum salt are water-soluble; The molecular weight of the polyethyleneimine is 8000-30000 Da; The mass ratio of polyethyleneimine to fumarate is 1:(5-15); The post-processing includes ultrasonic treatment and freeze drying.

[0008] This application also provides the following technical solutions: An AlFu-PEI metal-organic framework material was obtained by the aforementioned preparation method.

[0009] This application also provides the following technical solutions: The aforementioned AlFu-PEI metal-organic framework material is used in wastewater treatment; wherein the material is used to adsorb anionic dyes in wastewater.

[0010] The technical solution provided in this application has the following beneficial effects: (1) The preparation method provided in this application uses PEI with a high molecular weight to modify the AlFu metal-organic framework, which can increase the amino density in the material and thus improve the adsorption performance. In the post-processing, ultrasonic treatment and freeze-drying are used to achieve high loading, uniform dispersion and stable immobilization of PEI on the AlFu framework. At the same time, the molecular weight and amount of PEI are controlled within a reasonable range to effectively avoid pore blockage and performance deterioration of the material. The preparation method provided in this application obtains AlFu-PEI material with high specific surface area, abundant amino active sites, open pore structure and high stability by synergistically controlling the molecular weight of PEI, loading ratio and post-processing.

[0011] (2) The AlFu provided in this application PEI materials achieve excellent anionic dye adsorption performance through the synergistic effect of the following factors: (i) the abundant amino groups on the PEI molecular chain can be protonated and become positively charged in a near-neutral aqueous environment, generating strong electrostatic attraction with negatively charged anionic dyes (such as Congo Red); (ii) the amino groups in PEI can form hydrogen bonds or coordination interactions with functional groups such as sulfonic acid groups in dye molecules, enhancing selective adsorption; (iii) the high specific surface area and ordered pores of the AlFu framework provide ample space for dye molecule diffusion, and the modification of PEI does not block the pores, ensuring mass transfer efficiency. The AlFu provided in this application... PEI materials also possess excellent cycle stability, high efficiency in adsorbing different anionic dyes, and applicability in complex systems, making them promising for industrial application in the field of advanced dye wastewater treatment. Attached Figure Description

[0012] Figure 1 The image shows the Fourier transform infrared (FTIR) spectrum of the AlFu-PEI material prepared in Example 1.

[0013] Figure 2 Performance testing and morphology characterization results of the AlFu-PEI material prepared in Example 1 (a, nitrogen adsorption-desorption isotherm; b and c are scanning electron microscope (SEM) microstructure images at magnifications of 3000x and 30000x, respectively).

[0014] Figure 3 The adsorption amount-adsorption time curve of the AlFu-PEI material prepared in Example 1 for Congo red dye is shown.

[0015] Figure 4 The results show the cyclic regeneration performance test results of the AlFu-PEI material prepared in Example 1. Invention Details 1. Terminology Explanation All patents and other publications cited herein are incorporated herein in their entirety. In the event of any conflict between any description of terminology herein and any document incorporated herein by reference, this document shall prevail.

[0016] Numerical ranges can be represented by a hyphen "-" or a tilde "~", and their endpoints are included by default. Unless otherwise specified, the numerical types within the range include, but are not limited to, integers, non-integers, percentages, fractions, etc., and the numerical types are not limited by the specific representation of the endpoints.

[0017] The terms “including,” “containing,” and similar expressions have a non-restrictive meaning.

[0018] A “combination” of enumeration items means any two or more enumeration items used together, unless the combination is technically impossible or the context explicitly excludes it.

[0019] "AlFu-PEI" refers to aluminum fumarate modified with polyethyleneimine.

[0020] The terms "metal-organic framework" and "metal-organic structure" are used interchangeably, referring to a periodic coordination network structure formed by interconnecting metal nodes through organic ligands.

[0021] "Microporous materials" refer to porous solids with significant micropore structures, whose pore size is less than about 2 nm according to the classification of the International Union of Pure and Applied Chemistry (IUPAC).

[0022] "Mesoporous materials" refers to porous materials with medium-sized pore structures, whose pore sizes are classified by IUPAC as being in the range of approximately 2-50 nm.

[0023] The use of ordinal terms such as "first" or "second" to define a claim element does not necessarily indicate any priority, order, or hierarchy of that claim element relative to another claim element, nor does it indicate the chronological order of the method steps. These terms are merely used as markers to distinguish different claim elements with the same name (which would be indistinguishable without the ordinal term). Similarly, the use of marks such as a), b), i), or ii) in the claims does not necessarily indicate any priority, order, or sequence of implementation among the steps. Likewise, the use of these terms in the specification does not necessarily imply any necessary priority or order.

[0024] The molecular weight of the polymer is assumed to be the weight-average molecular weight. When the unit of molecular weight is not given, it is assumed to be Daltons (Da). Unless otherwise stated, the polymers in this application are assumed to be polydisperse, and their molecular weight is allowed to be within ±20% of a given value without affecting their technical performance.

[0025] "Salt" includes, but is not limited to, salts derived from inorganic acids and / or organic acids and / or inorganic bases and / or organic bases. The inorganic acids include, but are not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, etc. The organic acids include, but are not limited to, acetic acid, 2,2-dichloroacetic acid, adipic acid, alginic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, 4-acetaminophen, camphoric acid, camphor-10-sulfonic acid, decanoic acid, hexanoic acid, caprylic acid, carbonic acid, cinnamic acid, citric acid, cyclohexane, dodecyl sulfate, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, formic acid, fumaric acid, galactopyric acid, gentian acid, glucoheponic acid, gluconic acid, glucuronic acid, glutamic acid, glutamate, glutaric acid, 2- Oxyglutaric acid, glycerophosphate, glycolic acid, hippuric acid, isobutyric acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, mucoic acid, naphthalene-1,5-disulfonic acid, naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, dihydroxynaphthalic acid, propionic acid, pyroglutamic acid, pyruvic acid, salicylic acid, 4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid, tartaric acid, thiocyanate, p-toluenesulfonic acid, trifluoroacetic acid, undecenoic acid, etc. The inorganic bases include, but are not limited to: ammonia, sodium, potassium, lithium, calcium, magnesium, iron, zinc, copper, manganese, aluminum, etc. The organic bases include, but are not limited to: primary amines, secondary amines, tertiary amines, substituted amines (including naturally occurring substituted amines), cyclic amines, and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, diethanolamine, ethanolamine, dianophenoxylate, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydatidamine, choline, betaine, phenylethylamine, benzathine, ethylenediamine, glucosamine, methylglucamine, theobromine, triethanolamine, tromethamine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins, etc.

[0026] Solvents of salts are also included in the category of "salt". The solvent can be water, and the corresponding solvate is a hydrate, including but not limited to monohydrate, dihydrate, hemihydrate, sesquihydrate, trihydrate, tetrahydrate, etc. The solvent can also be an organic solvent.

[0027] "Water-soluble salt" refers to a salt that has a solubility of 0.01 g or more in 100 g of pure water at 20°C, preferably 1 g or more.

[0028] "Water-based media" refers to liquid media whose main component is water.

[0029] "Post-processing" refers to any one or more operations performed after the completion of the target reaction to obtain the final product from the reaction system. Exemplary post-processing includes, but is not limited to, the following operations and combinations thereof: solid-liquid separation (e.g., centrifugation, filtration, sedimentation, etc.), washing (e.g., removing impurities using water, alcohols and / or other inorganic / organic solvents), drying (e.g., removing moisture / solvent under conditions such as heating, atmospheric pressure, vacuum, spraying, freezing, etc.), grinding, ultrasonic treatment, mechanical vibration, etc.

[0030] Ultrasonic treatment refers to the application of ultrasonic energy to liquid suspensions or solid-liquid mixtures to achieve dispersion, homogenization, breakup, degassing, or to promote surface treatment of materials. Common ultrasonic equipment can be used for ultrasonic treatment, such as ultrasonic baths, ultrasonic probes / rods, and other commercially available ultrasonic vibration devices. The duration and power of ultrasonic treatment can be adjusted according to the material properties, system size, and desired effect.

[0031] Freeze-drying is a drying method that involves first freezing a solid / suspension system containing a solvent at a low temperature, and then sublimating the frozen solvent directly from the solid state under vacuum or reduced pressure to obtain a dry solid. Freeze-drying is also known as sublimation drying or vacuum freeze-drying. The general steps of freeze-drying include: i) Pre-freezing: cooling the solvent-containing system to below the freezing point of the solvent (and some crystalline phase substances) (e.g., ii) Primary drying: Maintaining the low temperature under vacuum or reduced pressure (e.g., 0.01 to 100 Pa or higher / lower) allows the solid solvent to sublimate directly and leave the solid; iii) Secondary drying: Increasing the temperature as needed to remove residual moisture / solvent. Freeze-drying time can range from several hours to tens of hours, depending on the system volume, solvent volume, and equipment performance.

[0032] "Congo Red" refers to the compound with CAS number 573-58-0.

[0033] "Rose red" refers to the compound with CAS number 632-69-9.

[0034] 2. Implementation Plan One embodiment of this application is as follows: A method for preparing an AlFu-PEI metal-organic framework material includes the following steps: a) The fumarate and aluminum salt are reacted in an aqueous medium to obtain a suspension; b) Add polyethyleneimine to the suspension to carry out the second reaction; c) After the second reaction is completed, post-processing is performed to obtain the AlFu-PEI metal-organic framework material; Both the fumarate and aluminum salt are water-soluble; The molecular weight of the polyethyleneimine is 8000-30000 Da; The mass ratio of polyethyleneimine to fumarate is 1:(5-15); The post-processing includes ultrasonic treatment and freeze drying.

[0035] In some specific implementations, the fumarate is selected from any one of sodium fumarate, potassium fumarate, ammonium fumarate, lithium fumarate, magnesium fumarate, calcium fumarate, and combinations thereof.

[0036] In some specific implementations, the aluminum salt is selected from any one of aluminum nitrate, aluminum chloride, aluminum sulfate, and combinations thereof.

[0037] In some specific implementations, the fumarate provides C4H2O4 2- With the Al provided by aluminum salts 3+ The molar ratio is (1-2):1.

[0038] In some specific implementations, the fumarate provides C4H2O4 2- With the Al provided by aluminum salts 3+ The molar ratio is (1-1.5):1.

[0039] In some specific implementation plans, the aqueous medium is pure water.

[0040] In some specific implementation schemes, the aqueous medium is deionized water, distilled water, or ultrapure water.

[0041] In some specific implementation schemes, the amount of aqueous medium used is 100-400 mL per gram of fumarate.

[0042] In some specific implementation schemes, the amount of aqueous medium used is 200-300 mL per gram of fumarate.

[0043] In some specific implementations, the first reaction is carried out by mixing an aqueous solution of fumarate with an aqueous solution of aluminum salt; the mixing method includes, but is not limited to: adding one aqueous solution to another aqueous solution by dripping or adding it in batches, or mixing the two aqueous solutions in parallel flow; the amount of the aqueous medium is the sum of the volumes of the aforementioned aqueous solutions.

[0044] In some specific implementation schemes, fumarate is added to an aqueous solution of aluminum salt, and the first reaction is carried out after complete dissolution.

[0045] In some specific implementation schemes, the aluminum salt is added to an aqueous solution of fumarate, and the first reaction is carried out after complete dissolution.

[0046] In some specific implementation schemes, fumarate and aluminum salt are added simultaneously to an aqueous medium and allowed to dissolve completely before the first reaction is carried out.

[0047] In some specific implementations, the first reaction is carried out at 15-30°C.

[0048] In some specific implementations, the first reaction is carried out at 20-25°C.

[0049] In some specific implementations, the reaction time of the first reaction is 0.5-3 hours.

[0050] In some specific embodiments, the molecular weight of the polyethyleneimine is any one of 8000 Da, 9000 Da, 10000 Da, 11000 Da, 12000 Da, 13000 Da, 14000 Da, 15000 Da, 16000 Da, 17000 Da, 18000 Da, 19000 Da, 20000 Da, 21000 Da, 22000 Da, 23000 Da, 24000 Da, 25000 Da, 26000 Da, 27000 Da, 28000 Da, 29000 Da, and 30000 Da.

[0051] In some specific embodiments, the mass ratio of polyethyleneimine to fumarate is any one of 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 and 1:15.

[0052] In some specific implementations, the second reaction is carried out at 40-80°C.

[0053] In some specific implementations, the second reaction is carried out at 55-65°C.

[0054] In some specific implementations, the second reaction is carried out at a pH of 6-8.

[0055] In some specific implementations, the second reaction is carried out at a pH of 6.5-7.5.

[0056] In some specific implementations, the reaction time of the second reaction is 1-4 hours.

[0057] In some specific implementations, the reaction time of the second reaction is 2-3 hours.

[0058] In some specific implementations, the power of the ultrasonic treatment is 200-500W.

[0059] In some specific implementations, the power of the ultrasonic treatment is 300-400W.

[0060] In some specific implementations, the duration of the ultrasonic treatment is 5-30 minutes.

[0061] In some specific implementations, the duration of the ultrasound treatment is 10-20 minutes.

[0062] In some specific implementations, the freeze-drying is carried out in a temperature range of -80°C to -10°C.

[0063] In some specific implementations, the freeze-drying is carried out in a temperature range of -40°C to -20°C.

[0064] In some specific implementations, the freeze-drying is carried out under pressure conditions of 0.1-100 Pa.

[0065] In some specific implementations, the freeze-drying is carried out under pressure conditions of 1-40 Pa.

[0066] Another implementation of this application is as follows: An AlFu-PEI metal-organic framework material is obtained by any of the aforementioned preparation methods.

[0067] In some specific implementations, the material exhibits a saturated adsorption capacity of not less than 700 mg / g for Congo red at 25°C and pH=7.

[0068] In some specific implementations, the material exhibits a saturated adsorption capacity of not less than 600 mg / g for rose red at 25°C and pH=7.

[0069] Another implementation scheme of this application is as follows: The application of any of the aforementioned AlFu-PEI metal-organic framework materials in wastewater treatment; wherein the material is used to adsorb anionic dyes in wastewater.

[0070] In some specific implementations, the anionic dye is Congo red or rose red. 3. Detailed Implementation The raw materials used in this application can be purchased or synthesized in-house. The following specific embodiments are used to further describe the implementation of the present invention and do not limit the scope of the invention.

[0071] Example 1 This embodiment uses the following steps to prepare AlFu-PEI material: 0.5 g of sodium fumarate was dissolved in 50 mL of deionized water to obtain solution A. 0.8 g of aluminum nitrate hydrate was dissolved in 50 mL of deionized water to obtain solution B. Solution B was added dropwise to solution A, and the mixture was stirred at room temperature for 1.5 hours. 0.05 g of PEI with a molecular weight of 10000 Da was added, the pH was adjusted to 7.0, and the reaction was continued at 60°C for 2.5 hours. After the reaction was complete, the mixture was centrifuged. The resulting solid was collected, washed three times with deionized water, and then sonicated at 400 W for 15 minutes. Subsequently, the solid was transferred to a freeze dryer (-25°C, 3 Pa) and dried for 24 hours to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:10.

[0072] Example 2 Following the preparation method of Example 1, 0.05 g of PEI with a molecular weight of 30000 Da was used, with other conditions remaining unchanged, to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:10.

[0073] Example 3 Following the preparation method of Example 1, 0.05 g of PEI with a molecular weight of 8000 Da was used, with other conditions remaining unchanged, to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:10.

[0074] Example 4 Following the preparation method of Example 1, 0.0333 g of PEI with a molecular weight of 10000 Da was used, with other conditions remaining unchanged, to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:15.

[0075] Example 5 Following the preparation method of Example 1, 0.1 g of PEI with a molecular weight of 10000 Da was used, with other conditions remaining unchanged, to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:5.

[0076] Comparative Example 1 Following the preparation method of Example 1, 0.05 g of PEI with a molecular weight of 10000 Da was used, dried in an oven at 60°C without ultrasonic treatment, while keeping other conditions unchanged, to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:10.

[0077] Comparative Example 2 Following the preparation method of Example 1, 0.05 g of PEI with a molecular weight of 50,000 Da was used, and other conditions remained unchanged to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:10.

[0078] Comparative Example 3 Following the preparation method of Example 1, 0.15 g of PEI with a molecular weight of 10000 Da was used, with other conditions remaining unchanged, to obtain AlFu-PEI material. The mass ratio of PEI to sodium fumarate was 1:3.3.

[0079] Example 6 This example characterizes the AlFu-PEI material prepared in Example 1. FTIR results ( Figure 1 The figure shows that at 3437cm -1 The appearance of the stretching vibration peak of NH in PEI at this location proves that PEI has been successfully modified onto the AlFu framework. Nitrogen adsorption-desorption test ( Figure 2 a) and SEM images ( Figure 2 b, 2c) indicate that the material has a high specific surface area (calculated to be approximately 1400 m²). 2 ( / g) and abundant porous structure.

[0080] Example 7 Four mg of the AlFu-PEI material prepared in Examples 1, 2, 3, 4, 5, Comparative Example 1, Comparative Example 2, or Comparative Example 3 was added to 100 mL of a 30 mg / L Congo red solution. The solution was incubated at 25°C and pH 7 with shaking at 150 rpm for 240 minutes. After filtration, the remaining Congo red concentration was measured, and the Congo red removal rate and saturated adsorption capacity were calculated. The adsorption capacity-adsorption time curve of the AlFu-PEI material prepared in Example 1 for Congo red dye is shown below. Figure 3 As shown.

[0081] The AlFu-PEI materials prepared in Examples 1-5 all exhibited excellent adsorption performance for Congo red, with removal rates all exceeding 90% and saturated adsorption capacities greater than 700 mg / g. In particular, the AlFu-PEI material prepared in Example 1 achieved a removal rate of up to 96.6% for Congo red and a saturated adsorption capacity of up to 724.6 mg / g. In contrast, the material performance of Comparative Examples 1-3 was significantly reduced, with removal rates all below 90%. Comparative Example 1 did not undergo ultrasonic treatment and used conventional oven drying instead of freeze drying, resulting in a saturated adsorption capacity of only 618.8 mg / g. This demonstrates that the post-treatment process, including ultrasonication and freeze drying, employed in this invention is crucial for achieving efficient loading of PEI on the AlFu metal-organic framework and improving material performance. Comparative Example 2, due to the use of excessively high molecular weight (50,000 Da) PEI, experienced pore blockage, resulting in a saturated adsorption capacity of only 647.1 mg / g. The saturated adsorption capacity of Comparative Example 3 was only 664.3 mg / g, indicating that excessive PEI dosage can also cause pore blockage and performance degradation in the material.

[0082] Table 1: Preparation parameters and adsorption performance test results of AlFu-PEI materials

[0083] Example 8 Following the test method described in Example 7, the AlFu-PEI material prepared in Example 1 was subjected to an adsorption test for rose red (30 mg / L). The results showed that the AlFu-PEI material prepared in Example 1 achieved a removal rate of 90.1% for rose red, with a saturated adsorption capacity of 675.75 mg / g.

[0084] Example 9 The AlFu-PEI material saturated with adsorption in Example 7 (Example 1) was desorbed by shaking with 50 mL of ethanol for 30 min, then washed with water until neutral, and repeated for the Congo red adsorption experiment. The results showed that after three adsorption-desorption cycles, the AlFu-PEI material prepared in Example 1 achieved Congo red removal rates of 96.6%, 96.13%, and 94.20%, respectively. Figure 4 The saturated adsorption capacity decreased from the initial 724.6 mg / g to 706.5 mg / g (i.e., the capacity retention rate exceeded 97% and the decay rate was less than 3%), demonstrating excellent cycling stability.

[0085] Example 10 A complex matrix simulated wastewater containing various inorganic salts (0.01 M each of NaCl and Na₂SO₄) and a small amount of surfactant (sodium dodecyl sulfate, 10 mg / L) was prepared, and Congo red (30 mg / L) was added. Adsorption tests were conducted using the AlFu-PEI material prepared in Example 1, following the method described in Example 7. The results showed that the material exhibited good adsorption performance for Congo red in the complex matrix simulated wastewater, with a removal rate of 90.5% and a saturated adsorption capacity of 678.75 mg / g.

Claims

1. A method for preparing an AlFu-PEI metal-organic framework material, characterized in that, Includes the following steps: a) The fumarate and aluminum salt are reacted in an aqueous medium to obtain a suspension; b) Add polyethyleneimine to the suspension to carry out the second reaction; c) After the second reaction is completed, post-processing is performed to obtain the AlFu-PEI metal-organic framework material; Both the fumarate and aluminum salt are water-soluble; The molecular weight of the polyethyleneimine is 8000-30000 Da; The mass ratio of polyethyleneimine to fumarate is 1:(5-15); The post-processing includes ultrasonic treatment and freeze drying.

2. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The fumarate is selected from any one of sodium fumarate, potassium fumarate, ammonium fumarate, lithium fumarate, magnesium fumarate, calcium fumarate, and combinations thereof, preferably sodium fumarate.

3. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The aluminum salt is selected from aluminum nitrate, aluminum chloride, aluminum sulfate, and combinations thereof, preferably aluminum nitrate; Optionally, the fumarate provides C4H2O4 2- With the Al provided by aluminum salts 3+ The molar ratio is (1-2):1, preferably (1-1.5):

1.

4. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The aqueous medium is pure water, preferably deionized water, distilled water, or ultrapure water; Optionally, the amount of the aqueous medium used is 100-400 mL, preferably 200-300 mL, per gram of fumarate.

5. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The first reaction is carried out at 15-30°C, preferably at 20-25°C; Optionally, the reaction time of the first reaction is 0.5-3 hours.

6. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The second reaction is carried out at 40-80°C, preferably at 55-65°C; Optionally, the second reaction is carried out at a pH of 6-8, preferably at a pH of 6.5-7.5; Optionally, the reaction time of the second reaction is 1-4 hours, preferably 2-3 hours.

7. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The power of the ultrasonic treatment is 200-500W, preferably 300-400W; Optionally, the duration of the ultrasonic treatment is 5-30 minutes, preferably 10-20 minutes.

8. The method for preparing the AlFu-PEI metal-organic framework material according to claim 1, characterized in that, The freeze-drying is carried out in a temperature range of -80°C to -10°C, preferably -40°C to -20°C; Optionally, the freeze-drying is carried out under pressure conditions of 0.1-100 Pa, preferably 1-40 Pa.

9. An AlFu-PEI metal-organic framework material, characterized in that, The material is obtained by the preparation method according to claim 1; Optionally, the material has a saturated adsorption capacity of not less than 700 mg / g for Congo red at 25°C and pH=7. Optionally, the material has a saturated adsorption capacity of not less than 600 mg / g for rose red at 25°C and pH=7.

10. The application of the AlFu-PEI metal-organic framework material according to claim 9 in wastewater treatment, characterized in that, The material is used to adsorb anionic dyes in wastewater; Optionally, the anionic dye is Congo Red or Rose Red.

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